1. Field of the Invention
The present invention relates to a pot type oil burner, and more particularly to a pot type oil burner capable of suppressing diffusion of an incomplete combustion gas generated during the extinction operation of the pot type oil burner into a room while preventing the generation of the same gas.
2. Description of the Related Art
In generally, when the pot type oil burner is to be extinguished, the supply of a fuel into a pot is stopped and a combustion fan for feeding combustion air into the pot and a convection fan for feeding blowing air into a room are maintained to be rotated, and the fuel remaining in the pot is continuously combusted, thereby burning out the fuel in the pot and thus carrying out the extinction. The rotation of the combustion fan and the convection fan is continued until a frame body of the burner and the pot reaches a low temperature so that the frame body can be prevented from reaching a high temperature. However, a bad odor is generated in a process for completely burning out the unburnt fuel.
Therefore, there has conventionally been proposed a technique for preventing the bad odor from being generated during the extinction of the pot type oil burner. In a technique described in Japanese Utility Model Publication No. 3-35956 (1991), a combustion fan and a convection fan for feeding air into a room together with a combustion gas are stopped immediately after an extinction operation. According to this technique, an incomplete combustion gas can be prevented from being flowing from a pot, and furthermore, oxidization of an unburnt gas remaining in the pot in a high temperature state is accelerated therein in order to suppress the generation of a bad odor. In the pot type oil burner, however, even if a very long time passes after the extinction operation is started, the fuel remaining in a fuel feeding pipe may enter into the pot in some cases. For this reason, when the fan are stopped as in the conventional art, the fuel is collected in the pot and it takes a long time to decrease the temperature of the pot. Therefore, a frame body having the pot accommodated therein is locally heated and is brought into a dangerous state.
According to the technique described in the Japanese Utility Model Publication No. 60-36833 (1985), the direction of rotation of an indoor fan is reversed during the extinction operation and a combustion gas is bllowed out from the back side of a frame body of a burner. In the conventional art, a bad odor (an unburnt gas) can be prevented from blown out toward the side of a user of the burner during extinction such that the user does not smell the bad odor or malodor. However, a driving motor capable of instantaneously reversing the rotational direction is a very special motor, and an inexpensive motor such as an AC induction motor to be generally used cannot be utilized.
Moreover, there has conventionally been proposed that the structure of the pot is devised to reduce a fuel remaining in a liquid state in the pot as much as possible, thereby lessening the amount of generation of the bad odor. However, this technique cannot sufficiently prevent the user from smelling the bad odor (incomplete combustion gas).
It is an object of the present invention to provide a pot type oil burner capable of preventing the user from being noticing or feeling the generation of an incomplete combustion gas.
It is another object of the present invention to provide a pot type oil burner capable of preventing a flame from going out during extinction operation, thereby lessening the amount of generation of the incomplete combustion gas.
It is a further object of the present invention to provide a pot type oil burner capable of preventing the user from noticing or feeling the generation of the incomplete combustion gas by using a fan having an inexpensive motor as a driving source.
A pot type oil burner to be improved by the present invention comprises a frame body having an air outlet in a front part thereof, a cylindrical bottomed pot provided in the frame body and having a large number of through holes for air flow on a peripheral wall, a combustion fan including a first motor as a driving source and serving to supply combustion air into the pot through the through holes, combustion fan control means for controlling rotation of the first motor, thereby controlling an amount of air flow from the combustion fan, fuel feeding means for feeding a fuel into the pot through a fuel feeding pipe, fuel feeding control means for controlling a driving operation of the fuel feeding means, an electric heater to be energized from a start of ignition to a start of combustion, thereby heating the pot, heater control means for controlling the energization to the electric heater, a convection fan including a second motor as a driving source, attached to the frame body to feed air from an outside of the frame body into the frame body and to blow out the air into a room through the air outlet together with a combustion gas discharged from the pot, fan control means for con+rolling rotation of the second motor, thereby controlling an amount of air flow from the fan, and a control command generator for giving a control command to the combustion fan control means, the fuel feeding control means, the heater control means and the convection fan control means, respectively.
In the present invention, the control command generator is operated in the following manner. First of all, the control command generator outputs a fuel feeding stop command for stopping the driving operation of the fuel feeding means to the fuel feeding control means and outputs a heater energization command to the heater control means, in order to energize the heater for a predetermined first time period which is longer than a time period required for completely ending combustion, when an extinction command is input. Moreover, the control command generator outputs a rotation decrease command for decreasing the rotation of the second motor to the convection fan control means so as to decrease the amount of air from the convection fan after a predetermined second time period equivalent to a time period to be considered to start incomplete combustion after the extinction command is input passes, while a predetermined third time period to be considered to be required for reducing a combustion flame or extinguishing the flame in the pot then passes. Then, the control command generator outputs a fan stop command for stopping the combustion fan and the convection fan to the combustion fan control means and the convection fan control means after the first time period is ended.
In the present invention, the supply of the fuel is stopped during the extinction operation. Originally, the electric heater which is used for only the ignition operation is also used for the extinction to heat the pot such that the combustion flame does not go out in the pot during the extinction operation. Accordingly, it is possible to almost completely combust the unburnt gas in the pot. After the extinction is completed, a cracked gas is generated if the fuel remains in the pot. Consequently, a bad odor having a hard irritating smell is sprayed onto a user through the wind of the convection fan. However, even if the fuel remaining in the fuel pipe enters the pot after the extinction is completed, the fuel is oxidized with the air fed into the pot through the combustion fan in the high temperature atmosphere heated by the electric heater. Consequently, it is possible to prevent the bad odor from being generated from the fuel remaining in the pot.
In the present invention, particularly, the rotational speed of the convection fan is decreased for a period in which incomplete combustion might be generated after the extinction operation is started (that is, in the third time period) or thereafter (after the combustion flame is reduced or the extinction is carried out). Consequently, the flow velocity of the air blown out of the air outlet of the frame body is decreased. As a result, the air containing an incomplete combustion gas is raised in the room space without reaching the user present in the forward part of the frame body. Therefore, it is hard for the user to notice the generation of the incomplete combustion gas. The degree of the decrease in the rotation of the convection fan belongs to the range of design items. It is preferable that the rotational speed should be decreased without locally raising the temperature of the frame body such that the air containing the combustion gas blown out of the air outlet can be raised upward as rapidly as possible or immediately.
After the combustion of the unburnt gas is completed, it is preferable that the rotational speed of the convection fan should be raised. Thus, the frame body and the pot can be cooled in the early stage.
It is preferable that the speed of the convection fan should be decreased in a short time. If the forced braking means is provided on the motor for the convection fan, the rotational speed of the convection fan can be forcedly decreased to be a low speed.
Moreover, the rotational speed of the convection fan may be maintained to be constant in a low speed region or may be reduced gradually However, if the rotational speed of the convection fan is reduced as required or more, there is a possibility that the temperature of the frame body might be raised excessively. The rotational speed of the motor to be used as the driving source of the convection fan is monitored by the rotational speed detecting means. If the rotational speed of the motor is decreased lower than a predetermined rotational speed, it is preferable that the rotational speed of the convection fan should be increased.
Moreover, when the combustion flame in the pot is reduced, the incomplete combustion gas is easily generated. Therefore, the flame detecting means for detecting a flame is used to detect the size or the height of the flame in the pot. If the size of the flame is smaller than a predetermined size, the rotational speed of the combustion fan maybe decreased. Thus, the extinction can be carried out with an almost good balance of an air/fuel ratio between the unburnt gas and the air. Consequently, the amount of generation of the incomplete combustion gas can be decreased. According to the pot type oil burner of the present invention, ignition and combustion in a normal combustion state are controlled in the same manner as a conventional product.
These objects as well as other objects, features and advantages of the present invention will become more apparent to those skilled in the art from the following description with reference to the accompanying drawings.